Remove vestigial 'sortlist' code

These were the remnants of the 'sortlist' option in resolv.conf, which
Android never supported and is superseded by RFC 3484 sorting.

Removing it will improve our test coverage scores because this code was
actually unreachable :-)

Test: atest
Change-Id: I2134dccd55be8ec977fd4aa8c047b82fb74e3769